package com.bigshen.algorithm.iHash.solution02CloneGraph;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * 133. Clone Graph
 * Given a reference of a node in a connected undirected graph.
 *
 * Return a deep copy (clone) of the graph.
 *
 * Each node in the graph contains a val (int) and a list (List[Node]) of its neighbors.
 *
 * class Node {
 *     public int val;
 *     public List<Node> neighbors;
 * }
 *  
 *
 * Test case format:
 *
 * For simplicity sake, each node's value is the same as the node's index (1-indexed). For example, the first node with val = 1, the second node with val = 2, and so on. The graph is represented in the test case using an adjacency list.
 *
 * Adjacency list is a collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a node in the graph.
 *
 * The given node will always be the first node with val = 1. You must return the copy of the given node as a reference to the cloned graph.
 *
 *Example 1:
 * Input: adjList = [[2,4],[1,3],[2,4],[1,3]]
 * Output: [[2,4],[1,3],[2,4],[1,3]]
 * Explanation: There are 4 nodes in the graph.
 * 1st node (val = 1)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
 * 2nd node (val = 2)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).
 * 3rd node (val = 3)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
 * 4th node (val = 4)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).
 *
 * 来源：力扣（LeetCode）
 * 链接：https://leetcode-cn.com/problems/clone-graph
 * 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
 * 来源：力扣（LeetCode）
 * 链接：https://leetcode-cn.com/problems/clone-graph
 * 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
 */


public class Solution {

    // Definition for a Node.
    class Node {
        public int val;
        public List<Node> neighbors;

        public Node() {
            val = 0;
            neighbors = new ArrayList<>();
        }

        public Node(int _val) {
            val = _val;
            neighbors = new ArrayList<Node>();
        }

        public Node(int _val, ArrayList<Node> _neighbors) {
            val = _val;
            neighbors = _neighbors;
        }
    }

    public Node cloneGraph(Node node) {

        if (null == node) {
            return null;
        }

        Map<Node, Node> map = new HashMap<>();
        cloneNode(node, map);
        return map.get(node);
    }

    private void cloneNode(Node node, Map<Node, Node> map) {
        if (null == node || map.containsKey(node)) {
            return;
        }
        Node cloneNode = new Node(node.val);
        map.put(node, cloneNode);

        List<Node> neighbors = node.neighbors;
        List<Node> cloneNeighbors = new ArrayList();

        if (null == neighbors) {
            return;
        }

        for (int i = 0; i < neighbors.size(); i ++) {
            Node element = neighbors.get(i);
            cloneNode(element, map);
            cloneNeighbors.add(map.get(element));
        }

        cloneNode.neighbors = cloneNeighbors;
    }

}
